The role of water in many multi-component interfaces is of great interest for both technological and environmental applications. Using Sum Frequency Generation (SFG), buried, air and vacuum interfaces can be probed to characterize these interactions. With this nonlinear spectroscopy, we can obtain surface-sensitive information where the signal intensity is proportional to the absolute square of the surface response. Summing the surface responses for discrete resonances and then taking the absolute square to obtain the SFG intensity leads to an interference among nearby resonances. This interference masks small resonances, shifts peak frequencies, causes the loss of molecular orientation information and an inability to measure surface concentrations. For these reasons, interference makes spectral deconvolution difficult. In using a nonlinear interferometer, where SFG is simultaneously and independently generated from a sample and a reference, many of these limitations can be overcome. A nonlinear interferometer has been used to better understand the molecular conformations of silanized surfaces. Conformations studied include how Octadecyltrichlorosilane (OTS) monolayer is altered in the presence of water, as well as other interfaces of environmental importance.

Water in hydrophobic and other environmental multi-component interfaces

2019 Fall National Meeting

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